Use rb_ensure instead of guard objects for Dir.pwd

This replaces GC-based buffer guards (rb_imemo_tmpbuf,
TypedData_Wrap_Struct) with rb_ensure to clean up malloc/xmalloc memory
when an exception occurs.

Author: jhawthorn

dir.c

@@ -1586,23 +1586,29 @@ dir_chdir(VALUE dir)
 }
 
 #ifndef _WIN32
-VALUE
-rb_dir_getwd_ospath(void)
+static VALUE
+getcwd_to_str(VALUE arg)
 {
-    char *path;
-    VALUE cwd;
-    VALUE path_guard;
-
-    path_guard = rb_imemo_tmpbuf_new();
-    path = ruby_getcwd();
-    rb_imemo_tmpbuf_set_ptr(path_guard, path);
+    const char *path = (const char *)arg;
 #ifdef __APPLE__
-    cwd = rb_str_normalize_ospath(path, strlen(path));
+    return rb_str_normalize_ospath(path, strlen(path));
 #else
-    cwd = rb_str_new2(path);
+    return rb_str_new2(path);
 #endif
-    rb_free_tmp_buffer(&path_guard);
-    return cwd;
+}
+
+static VALUE
+getcwd_xfree(VALUE arg)
+{
+    xfree((void *)arg);
+    return Qnil;
+}
+
+VALUE
+rb_dir_getwd_ospath(void)
+{
+    char *path = ruby_getcwd();
+    return rb_ensure(getcwd_to_str, (VALUE)path, getcwd_xfree, (VALUE)path);
 }
 #endif
 

util.c

@@ -529,45 +529,43 @@ ruby_strdup(const char *str)
 char *
 ruby_getcwd(void)
 {
-    VALUE guard = rb_imemo_tmpbuf_new();
     int size = 200;
     char *buf = xmalloc(size);
 
     while (!getcwd(buf, size)) {
         int e = errno;
         if (e != ERANGE) {
-            rb_free_tmp_buffer(&guard);
+            xfree(buf);
             rb_syserr_fail(e, "getcwd");
         }
         size *= 2;
-        rb_imemo_tmpbuf_set_ptr(guard, buf);
-        buf = xrealloc(buf, size);
+        xfree(buf);
+        buf = xmalloc(size);
     }
-    rb_imemo_tmpbuf_set_ptr(guard, NULL);
     return buf;
 }
 
 # else
 
-static const rb_data_type_t getcwd_buffer_guard_type = {
-    .wrap_struct_name = "ruby_getcwd_guard",
-    .function = {
-        .dfree = free // not xfree.
-    },
-    .flags = RUBY_TYPED_FREE_IMMEDIATELY | RUBY_TYPED_WB_PROTECTED
-};
+static VALUE
+getcwd_strdup(VALUE arg)
+{
+    return (VALUE)ruby_strdup((const char *)arg);
+}
+
+static VALUE
+getcwd_free(VALUE arg)
+{
+    free((void *)arg);
+    return Qnil;
+}
 
 char *
 ruby_getcwd(void)
 {
-    VALUE guard = TypedData_Wrap_Struct((VALUE)0, &getcwd_buffer_guard_type, NULL);
-    char *buf, *cwd = getcwd(NULL, 0);
-    RTYPEDDATA_DATA(guard) = cwd;
+    char *cwd = getcwd(NULL, 0);
     if (!cwd) rb_sys_fail("getcwd");
-    buf = ruby_strdup(cwd);	/* allocate by xmalloc */
-    free(cwd);
-    RTYPEDDATA_DATA(RB_GC_GUARD(guard)) = NULL;
-    return buf;
+    return (char *)rb_ensure(getcwd_strdup, (VALUE)cwd, getcwd_free, (VALUE)cwd);
 }
 
 # endif